The present invention generally relates to shallow well centrifugal pumps and, more particularly, is concerned with a unique venturi nozzle assembly construction in a shallow well pump casing.
Centrifugal or impeller type pumps are widely used in pumping systems, particularly in well pumping systems. The pumps used in well pumping systems are generally of two types, shallow well pumps and deep well pumps. The shallow well type pump is commonly used with wells having a depth from ground surface to water surface of about 25 feet or less and is typically located on the ground surface. Only a water intake or suction pipe to the pump extends into the well to below the water surface.
Representative pumps proposed in the prior art for use in wells and other applications are the ones disclosed in U.S. Pats. Nos. to Da Col (2,272,906), Ruth (2,403,556), Patterson (2,524,269), Conery (2,615,397), Smith (2,700,338), Lung (2,786,417), Carpenter (2,853,014), Bliss (2,911,916), Hall (2,941,474), Schipper (2,987,002), Stanley et al. (3,063,377) and Jensen et al. (4,627,792). A typical construction of a shallow well centrifugal pump is disclosed in the Ruth patent. The pump basically includes an electric motor, a housing or casing having a water suction inlet and discharge outlet, an impeller, a diffuser, and an arrangement of a venturi tube and nozzle. The diffuser is supported stationarily in the casing adjacent its discharge outlet. The impeller, which is rotatably driven by the motor, is disposed within the diffuser. The venturi tube and nozzle arrangement extends between and is mounted to the casing suction inlet and to the diffuser inlet which communicates with the center of the impeller. The venturi tube is disposed to receive water supplied from the well, via the suction pipe, through the suction inlet of the casing and water which is recirculated from the impeller, via the casing, through the nozzle. The combined action of high velocity rotation of the impeller and high pressure recirculation of a fraction of its water output via the casing through the nozzle to the venturi tube produces a vacuum condition at the suction inlet of the casing that then allows atmospheric pressure to supply or push water through the suction pipe from the bottom of the shallow well to the casing suction inlet and feed water therefrom through the venturi tube to the impeller inlet and out through the discharge outlet.
For the most part, historically, shallow well centrifugal pumps of the above-described typical construction have operated reasonably well and have generally achieved the level of performance for which they were designed. However, pumps of this general construction have certain drawbacks which make them less than an optimum design. One drawback is that the pump casing and a tube which supports the nozzle are frequently fabricated as a one-piece casting which requires slow, complicated and expensive fabrication steps. Another typical drawback is that the venturi tube and nozzle are oftentimes mounted to the casing and/or the diffuser by being threadably attached thereto. Provision of the threads necessary to accomplish attachment in this manner may further require additional time-consuming and expensive steps to be carried out to produce screw threads on the venturi tube, nozzle, casing and diffuser. Still another drawback is that threaded connections make it difficult to properly locate certain components, such as the venturi tube and nozzle, relative to one another. As can be appreciated, this can be critical to the performance of the pump. Yet another time-consuming drawback is that threaded connections require the use of tools for assembly and disassembly of the components. A further drawback is that threaded connections can accumulate and hide foreign matter and prevent components from fitting together to their proper relative locations. Finally, screw threads do not always seal properly and cross-threading can easily occur between threads of plastic components and those of cast metal components.
Consequently, in view of the representative foregoing described drawbacks, it is readily apparent that a need still remains for many improvements in shallow well centrifugal pump construction.